1. Field of the Invention
The present invention relates to fireplaces used for clean burning solid fuels. More particularly, the present invention relates to a novel zero clearance fireplace which automatically clean burns solid fuels such as wood at different rates of combustion using a novel primary and a novel secondary combustion air system to maintain pyrolytic temperatures.
2. Description of the Prior Art
In our U.S. Pat. No. 4,793,322 a zero clearance fireplace is shown and described which has a highly efficient heat exchanger combined with a gas burner system that meets all of the American National Standard Institute's specifications for gas appliances in ANSI Specification Z21.50 and Z21.60. These specifications have been adapted by the American Gas Association (AGA) design certification standards group for direct vented multi-glass fireplaces. In our U.S. Pat. No. 5,016,609 there is shown and described a direct vented zero clearance fireplace to be used with gas burning systems. This gas burning fireplace was designed for high BTU output and for use with multi-glass side walls and yet produce high efficiency with low carbon monoxide meeting all of the requirements of the ANSI and AGA specifications.
The two above mentioned patents relate to clean burning high efficiency gas heating systems. The latest Clean Air Act mandates pollution standards for wood burning fireplaces and stoves. In addition to the Federal Clean Air Standards that become more stringent and difficult to meet over a period of years, state and local codes have become, and are becoming, even tighter and more stringent than the federal law which is now defined in the Safety and Environmental Standards as set forth in EPA Phase II, 1990. In many western and mid-western cities such as Fresno, Calif., Reno, Nev., Denver, Colo. and numerous other local communities there have been promulgated standards that cannot be met by all existing wood burning zero clearance fireplaces and most wood burning stoves. The owners of such fireplaces and stoves are faced with the possibility of having such fireplaces and stoves replaced or their use discontinued.
Therefore it would be extremely desirable to provide a novel high efficiency clean burning zero clearance fireplace for solid fuels which would meet all of the above mentioned standards.